1. Field of the Invention
This application relates to an electrical connector and a terminal for use in the electrical connector of the type suitable for use in establishing an interconnector to traces on a circuit panel, especially to an electrical connector socket for use in establishing electrical interconnections to a single in-line memory module.
2. Description of the Prior Art
Single in-line memory modules represent a high density, low profile single in-line package for electronic components such as dynamic random access memory integrated circuit components. A plurality of these components can be mounted in line on a circuit panel whose height is little more than the length of the components themselves. The circuit panels can in turn be mounted on a printed circuit board daughtercard which can then be mounted on a printed circuit board mothercard. The spacing between adjacent daughtercards would then need to be only slightly greater than the height of the individual circuit panels or single in-line memory modules.
One approach for mounting single in-line memory modules on a daughterboard would be to employ plug in leads adjacent one edge of the circuit panel. These plug in leads can then be connected to conventional printed circuit board contacts such as miniature spring contacts.
An alternate approach has been to use single in-line memory module sockets to establish a disconnectable interconnection to traces along the edge of the circuit panel used in the single in-line memory module. Terminals for use in such sockets are disclosed in U.S. Pat. Nos. 4,557,548 and 4,558,912. Additional details of an insulative housing which is suitable for use with those terminals is disclosed in U.S. Pat. 4,781,612. The socket disclosed in these patents is intended for use with in-line memory modules having a center line spacing for pads or traces at the edge of the circuit panel of 0.100 inch. Since the terminals employed in that socket are stamped and formed, the width of the terminals generally precludes establishing an interconnection on closer center line spacings.
Instead of using stamped and formed terminals, other single in-line memory module sockets employ edge stamped terminals. For example, U.S. Pat. No. 4,737,120 discloses an electrical connector of the type suitable for use in a single in-line memory module in which a zero insertion force interconnection is established between the terminals and the pads on the circuit panel. The circuit panel is inserted at a angle and then cammed into position. The insulative housing on the connector provides a stop to hold the circuit panel in position. Another zero insertion force connector is disclosed in U.S. Pat. No. 4,575,172. The contact terminals in each of these patents is edge stamped sockets using terminals of this type are suitable for use on center line spacings on the order of 0.050 inches.
Each of these zero insertion force configurations provides limited wipe between the contacts and the pads on the printed circuit board. It is understood that full force wipe is desirable in order to remove contaminates which may build up either on the terminals or on the printed circuit board pads or traces. U.S. Pat. No. 4,725,250 discloses a socket connector employing a terminal in which a full force wiping action is established between the terminals and the surface pad portions of traces on the circuit panel. This connector also includes edged stamped terminals. The connector shown in U.S. Pat. No. 4,725,250 is suitable for use with standard single in-line memory modules. However, not all commercially available single in-line memory modules are manufactured in compliance with generally accepted standards for such modules, such as appropriate JEDEC standards. Nonstandard single in-line memory module circuit panels are manufactured with the pad portions of the traces adjacent the edge of the circuit panel being shorter than required by industry acknowledged standards. The connector disclosed in U.S. Pat. No. 4,725,250 is unsuitable for use with circuit panels having short pad portions where contact must be established immediately adjacent the edge of the circuit panel because of the height of the beams used to establish the full force wipe contact in that connector.
Deviations in JEDEC standards have also occurred because some module manufacturers have been unable to maintain a tolerance of .+-.0.003 inches on the module thickness as required by JEDEC. Tolerances of .+-.0.008 inches are more realistic; but such tolerances complicate the design of the terminal because a larger deflection range is necessary. Lengthening the terminals is not suitable because the improved density offered by SIMM's is compromised and contact cannot be established adjacent the edge of the module.
Not only have non-conforming single in-line memory modules begun to appear, but the basic single in-line memory module socket is being adapted to applications in which additional integrated circuit components are positioned on the circuit panel. Indeed the height of the circuit panel has been increasing as more and more integrated circuit packages are added to the modules. Modules referred to as SAM's (special application modules) using the basic SIMM approach. For instance, boards using the SIMM approach now have a height of 2.0 to 3.5 inches. The additional height of these circuit panels, makes it difficult for standard sockets to stabilize these components since conventional panel guides used in such sockets do not have a height sufficient to engage these circuit panels adjacent there upper end. The instant invention provides not only a means for stabilizing circuit panels having a greater height, but also employs a terminal suitable for establishing electrical contact adjacent the edge of the circuit panels so that this full force wipe connector can be employed with non-standard single in-line memory module circuit panels.